The present invention relates to an accessory mainly composed of silver, and a silver alloy for the accessory.
As silver alloys mainly composed of silver, those for electric contacts, those for accessories, and the like have conventionally been known; whereas publications such as Japanese Patent Application Laid-Open No. SHO 53-43620, Japanese Patent Application Laid-Open No. SHO 57-114631, Japanese Patent Application Laid-Open No. SHO 58-104146, Japanese Patent Application Laid-Open No. SHO 60-258439, Japanese Patent Application Laid-Open No. SHO 61-6238, Japanese Patent Application Laid-Open No. SHO 62-20850, Japanese Patent Application Laid-Open No. SHO 63-14830, and Japanese Patent Application Laid-Open No. HEI 7-166269, for example, have been known to disclose these silver alloys.
First, Japanese Patent Application Laid-Open No. SHO 53-43620 discloses a silver alloy for use in wristwatch belts and the like, which comprises silver as a base material and contains palladium, tin, zinc, aluminum, and the like in addition to germanium and indium.
Japanese Patent Application Laid-Open No. SHO 57-114631 discloses a silver alloy for dental use, which comprises silver as a base material and contains palladium, copper, and the like in addition to germanium or indium.
Japanese Patent Application Laid-Open No. SHO 58-104146 discloses a silver alloy for use in sliding contacts of commutators, which comprises silver as a base material and contains indium, or comprises silver as a base material and contains bismuth and the like in addition to indium.
Japanese Patent Application Laid-Open No. SHO 60-258439 discloses a silver alloy for dental use, which comprises silver as a base material and contains palladium, copper, zinc, and the like in addition to germanium and indium.
Japanese Patent Application Laid-Open No. SHO 61-6238 discloses a silver alloy for use in sliding contacts of commutators, which comprises silver as a base material and contains cadmium and the like in addition to indium and germanium.
Japanese Patent Application Laid-Open No. SHO 62-20850 discloses a silver alloy for use in art and craft products, accessories, and the like, which comprises silver as a base material and contains zinc, boron, and the like in addition to germanium. It also discloses one which comprises silver as a base material and contains tin, zinc, and the like in addition to indium.
Japanese Patent Application Laid-Open No. SHO 63-14830 discloses a silver alloy for use in wristwatches, rings, pendants, tableware, and the like, which comprises silver as a base material and contains platinum, tin, zinc, and the like in addition to germanium and indium.
Japanese Patent Application Laid-Open No. HEI 7-166269 discloses a silver alloy for use in sliding contacts of commutators, which comprises silver as a base material and contains copper, palladium, bismuth, and the like in addition to indium and germanium.
Each of the above-mentioned conventional techniques comprises silver as a base material, contains germanium or indium, and has a suitability for dental use, electric contacts, or common accessories.
Apart from the silver alloys for dental use and electric contacts, those for common accessories disclosed in Japanese Patent Application Laid-Open No. SHO 53-43620, No. SHO 62-20850, and No. SHO 63-14830 have problems as follows. Namely, the silver alloy of Japanese Patent Application Laid-Open No. SHO 53-43620 is likely to be oxidized since it contains aluminum, the silver alloy of Japanese Patent Application Laid-Open No. SHO 62-20850 is materially unstable since boron is used therein, and the silver alloy of Japanese Patent Application Laid-Open No. SHO 63-14830 is expensive since platinum is used therein.
Meanwhile, known as accessories are not only those such as rings and pierced earrings mainly aimed at aesthetically decorating bodies and those such as wristwatch belts mainly aimed at attaching an article (the main part of a watch) having a specific function to a body, but also health-oriented type accessories secondarily or mainly aimed at the improvement of health and predetermined curing/healing effects.
However, such conventional accessories in which health, cure, and the like are taken into consideration contain germanium as their main ingredient and are different from those mentioned above that are aimed at decoration. For example, the one described in Japanese Patent Publication No. SHO 58-48186 is configured such that a solid piece of N-type, intrinsic, or P-type germanium comes into contact with a skin with the aid of a member such as tape, and is assumed to be capable of killing pains and sedating inflammations due an electric action.
Though various studies have been made in addition to the above-mentioned conventional techniques, no silver alloys have yet been provided which are suitable for accessories expected to be effective in the improvement of health and the like while being used in contact with a skin. Namely, no silver alloys have been provided which takes account of the far-infrared effect inherent in germanium, i.e., the fact that germanium can exhibit a health-improving and curing effect for curing/healing stiff shoulders and the like.
Therefore, the inventor has repeated diligent studies and, as a result, has invented a novel silver alloy for accessories which is suitable for a constituent material for an accessory having both of a decorating function and a health-improving or curing/healing function.
Considering that a silver alloy suitable for a constituent material for an accessory having both of a decorating function and a health-improving or curing/healing function needs to satisfy the following first to fifth demands, the inventor has repeated various studies.
The first of demands is that it has a brightness and luster sufficient as a material of an accessory attached to a body; the second is that it is excellent in processibility as an accessory, i.e., it has appropriate degrees of hardness, ductility, and malleability; the third is that it is excellent in resistance to oxidation and other resistances to corrosion; the fourth is that it is a safe material to be used in contact with a body without needing excessively expensive components; and the fifth is that it fully exhibits the far-infrared effect inherent in germanium, i.e., the health-improving and curing effect for curing/healing stiff shoulders and the like.
According to the inventor""s studies, the silver alloy for accessories satisfying such demands comprises 1% to 9% by weight of germanium, 2% to 20% of indium in terms of weight ratio with respect to germanium, and the rest constituted by silver.
First, the silver alloy for accessories in accordance with the present invention can realize a brightness and luster suitable for an accessory attached to a body since it contains an appropriate amount of germanium. Namely, though it will have a silver-gray tint if germanium is less than 1% by weight, a brightness and luster similar to those of platinum can be obtained if the germanium content is 1% by weight or greater.
Second, it can improve the processibility as an accessory since it contains an appropriate amount of indium with respect to germanium. Namely, though an alloy of silver and germanium is likely to be brittle even if the amount of germanium is small, appropriate hardness, ductility, and malleability can be attained until the germanium content reaches approximately 9% by weight if an appropriate amount (2% to 20% in terms of weight ratio with respect to germanium) of indium is added thereto.
Third, while an alloy of silver and germanium is superior to pure silver in resistances to corrosion such as resistance to sulfurization, the resistance to oxidization and other resistances to corrosion can further be improved if indium is further added to this alloy. For example, while an accessory is exposed to sweat containing moisture, salts, and the like when used in contact with a body for a long period of time, it is less likely to yield corrosion and discoloration. If aluminum is added thereto, by contrast, it will be disadvantageous in that the alloy is more likely to be oxidized.
Fourth, each of silver, germanium, and indium is a safe material to be used in contact with a skin, whereas cadmium, for example, cannot be used in accessories. Though platinum or the like has a high security, the cost tends to increase when it is used.
Fifth, it can fully exhibit the far-infrared effect inherent in germanium, i.e., the health-improving and curing effect for curing/healing stiff shoulders and the like. The far-infrared effect of germanium is effectively exhibited in particular when microcrystals of germanium are formed in the base material of silver. This is because of the fact that microcrystals of germanium have a semiconductor-like property since they are crystals in spite of their minuteness. According to inventor""s experiments, only a small amount of microcrystals are formed when germanium is less than 1% by weight, whereas the constituting ratio of microcrystals decreases if the germanium amount is 9% by weight or greater on the contrary. Therefore, it is desirable that germanium be contained by at least 1% by weight but less than 9% by weight.
While the far-infrared effect of germanium is quite remarkably exhibited when germanium is a P-type semiconductor as compared with the case where it is an N-type or intrinsic semiconductor, indium is a III-group element and becomes an acceptor when added to a semiconductor, thus yielding P type. While silver acts as a donor with respect to germanium, thus yielding N type, on the other hand, its solubility is not greater than ⅓ that of indium. Therefore, if indium is used as a doping element, then P type is eventually realized. While boron and zinc may be considered as P-type impurities, boron is unfavorable in that it has such a small atomic radius that it is easy to get into and out from between atoms and is unstable. Zinc is hard to realize P type since its solubility is low.
The accessory of the present invention is characterized in that an outer surface thereof coming into contact with a skin while being worn on a body is constituted by a silver alloy for accessories, which will be explained later. While examples of accessories coming into contact with a skin in a state worn on a body include necklace, bracelet, wristband, ring, and wristwatch, they may be totally formed from the silver alloy for accessories of the present invention, or the plated layer on the surface thereof may be formed from the silver alloy for accessories of the present invention.
Preferably, the silver alloy for accessories in accordance with the present invention may contain at least 1.4% by weight a of germanium. As a consequence, while it is mainly composed of silver which is inexpensive as a rare metal, a brightness similar to that of platinum is favorably realized, and the ratio of microcrystallization of germanium can be made higher.
The silver alloy for accessories in accordance with the present invention may contain less than 5% by weight of germanium. As a consequence, the amount of germanium remaining in an atomic state without being microcrystallized can be made smaller.
Preferably, the silver alloy for accessories in accordance with the present invention may be such that the weight ratio of indium with respect to germanium is at least 5%. As a consequence, the far-infrared effect caused by P-type germanium can further be improved while further improving its processibility.
Preferably, the silver alloy for accessories in accordance with the present invention may be such that the weight ratio of indium with respect to germanium is less than 13%. As a consequence, the far-infrared effect caused by P-type germanium can further be improved while hardness can be secured when used in an accessory.